Welcome to the Shopify Community and great question. While I'm not an app developer myself, I'd be happy to share the links to our Shopify Partner earnings page if you haven't seen this already. This page breaks down in detail how our Partners earn money. Specifically, you can view the section on Shopify Apps. We also have a helpful Shopify Partners FAQ page that can help answer other questions you may have about the Partner Program.
Aside from this, hopefully some of our app developers will comment here on their tactics for ensuring their apps profit.
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